I can't think of any lighting that would be sufficient for an anemone for the $300 range unless you find something used on Craigslist or from a reef club member. A 6 or 8 bulb
HO T5 fixture would probably work, but it won't be that cheap. Metal halide would be the best option for keeping an anemone in a 55 gallon tank, but anything you find new for $300 wouldn't be worth buying.
Would you mind if I asked why keeping an anemone is such a big deal? You can get a similar look with a frogspawn coral if it's the aesthetics. Clownfish don't need one if that's the issue. Anemones need a mature tank (8+ months post-setup) and can cause big trouble for you if they aren't happy. Unhappy anemones will roam around the tank, and can sting coral or worse, meet an untimely end in a
powerhead and nuke your tank. Just a thought.